The ALMA REBELS Survey: cosmic dust temperature evolution out to z ∼ 7. Issue 3 (3rd February 2022)

• Record Type: Journal Article
• Authors: Sommovigo, L; Ferrara, A; Pallottini, A; Dayal, P; Bouwens, R J; Smit, R; da Cunha, E; De Looze, I; Bowler, R A A; Hodge, J; Inami, H; Oesch, P; Endsley, R; Gonzalez, V; Schouws, S; Stark, D; Stefanon, M; Aravena, M; Graziani, L; Riechers, D; Schneider, R; van der Werf, P; Algera, H; Barrufet, L; Fudamoto, Y; Hygate, A P S; Labbé, I; Li, Y; Nanayakkara, T; Topping, M
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 513:Issue 3(2022)
• Page Start: 3122
• Page End: 3135
• Publication Date: 2022-02-03
• Subjects: methods: analytical -- methods: data analysis -- dust, extinction -- galaxies: high-redshift -- infrared: ISM; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac302
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: ALMA observations have revealed the presence of dust in the first generations of galaxies in the Universe. However, the dust temperature T d remains mostly unconstrained due to the few available FIR continuum data at redshift $z$ > 5. This introduces large uncertainties in several properties of high-$z$ galaxies, namely their dust masses, infrared luminosities, and obscured fraction of star formation. Using a new method based on simultaneous [C $\scriptstyle \rm II$ ] 158-μm line and underlying dust continuum measurements, we derive T d in the continuum and [C $\scriptstyle \rm II$ ] detected $z$ ≈ 7 galaxies in the ALMA Large Project REBELS sample. We find 39 < T d < 58 K, and dust masses in the narrow range M d = (0.9−3.6) × 10 7 M⊙ . These results allow us to extend for the first time the reported T d ($z$ ) relation into the Epoch of Reionization. We produce a new physical model that explains the increasing T d ($z$ ) trend with the decrease of gas depletion time, t dep = M g /SFR, induced by the higher cosmological accretion rate at early times; this hypothesis yields T d ∝ (1 + $z$ ) 0.4 . The model also explains the observed T d scatter at a fixed redshift. We find that dust is warmer in obscured sources, as a larger obscuration results in more efficient dust heating. For UV-transparent (obscured) galaxies, T d only depends on the gas column density (metallicity), $T_{\rm d} \propto N_{\rm H}^{1/6}$ ( T d ∝ Z −1/6 ). REBELS galaxies are on average relatively transparent, with effective gas column densities around N H ≃ (0.03−1) × 10 21 cm −2 . We predict that other high-$z$ galaxies (e.g. MACS0416-Y1, A2744-YD4), with estimated T d ≫ 60 K, are significantly obscured, low-metallicity systems. In fact, T d is higher in metal-poor systems due to their smaller dust content, which for fixed L IR results in warmer temperatures.